The present invention relates to a method of heat-treating an amorphous magnetic material, and more particularly to a method for readily obtaining an amorphous magnetic material having a high flux density and a high magnetic permeability.
An amorphous magnetic material attracts public attention for the reasons that it has a high magnetic permeability without any magnetic anisotropy resulted from a crystal structure. Especially, there is an amorphous magnetic material containing cobalt Co as their main component with a composition having a saturation magnetostriction constant .lambda..sub.s nearly equal to zero, and the application of such a material to a magnetic head has been energetically studied. In a conventional method for obtaining an amorphous material having a high magnetic permeability from an alloy which contains cobalt as its main component and has no magnetostriction, it is required that the alloy has a composition making its Curie temperature T.sub.c lower than its crystallization temperature T.sub.x, and is held at a temperature T.sub.a satisfying a relation T.sub.c &lt;T.sub.a &lt;T.sub.x for a predetemined period to remove thermal strain generated in forming the amorphous material. In more detail, the above-mentioned temperature T.sub.x indicates a crystallization starting temperature in the case where the temperature of the alloy is raised at a rate of about 5.degree. C./min. When the alloy is held at a temperature higher than or equal to the crystallization starting temperature T.sub.x, the crystallization generally proceeds, and its magnetic characteristic is deteriorated. However, in the case where the alloy having a composition making the Curie temperature T.sub.c lower than the crystallization starting temperature T.sub.x is heat treated in the manner described above, the saturation flux density B.sub.s of the alloy is 9.0 KG at most, and therefore the alloy does not suffice to form a magnetic head capable of satisfying recent demand for high recording density. In order to solve this problem, various devices have been hitherto made. For example, heat treatment of a magnetic material in a rotating magnetic field or other means have been used as a method for obtaining an amorphous material having a high magnetic permeability by heat treatment at a temperature lower than the crystallization temperature T.sub.x (and of course below Curie temperature T.sub.c) of the magnetic material. However, the above-mentioned heat treatment in a rotating field is required to rotate a magnetic field, and has many difficulties when viewed from a practical standpoint.